Abstract

A yaw plane model with limited roll DOF of a five-axle tractor semitrailer is developed to study the open-loop directional dynamics of the vehicle. A comprehensive driver model incorporating path preview, low and high frequency compensatory gains and time delays, and prediction of tractor lateral acceleration, articulation rate of the combination and the trailer sprung mass roll angle is developed and integrated with the vehicle model. The coupled driver-vehicle model is analyzed to explore the performance potentials of the vehicle design adapted for control limits of the driver. The data reported in the published studies are reviewed to identify range of control limits of the drivers in terms of preview distance, reaction time and compensatory gain. A comprehensive performance index including the path tracking, vehicle dynamic response characteristics and the driver’s steering effort is formulated and minimized using Gauss-Newton method to derive the desirable ranges of the vehicle parameters, including geometric, inertial, suspension, tire and the fifth wheel. The results of the study revealed that a driver with higher skill can easily adapt the vehicle with large size, soft suspension and relative over-steer nature. The adaptability of the vehicle is further examined for different drivers with varying skills. It is concluded that the adaptability and thus the directional performance of the vehicle can be enhanced through variations in the weights and dimensions, and suspension, tire and the fifth wheel properties. The results further show that the driver-adapted vehicle yields up to 33% reduction in the steering effort demand posed on the driver, while the roll angle and yaw rate response decrease by up to 40%.

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